Pressure Vessel

ABSTRACT

The present disclosure provides a pressure vessel 10 (sometimes known as a composite overwrapped pressure vessel or “COPV”) comprising carbon fiber 20 (such as carbon fiber 20 filaments) wrapped around a tank liner 30.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application a continuation of, and claims priority to, and thebenefit of, U.S. application Ser. No. 14/525,645 titled “PressureVessel,” filed Oct. 28, 2014, which claims the benefit of, and priorityto, pending U.S. Provisional Application No. 61/945,220 filed Feb. 27,2014 titled “Pressure Vessel.”

FIELD OF THE DISCLOSURE

The present disclosure pertains to vessels for the transport ofpressurized gases and liquids. More specifically, in one embodiment, thepresent disclosure pertains to vessels for the transport and storage ofcompressed natural gas (“CNG”), propane, methane, alcohol, helium,hydrogen or argon.

BACKGROUND

The desire to supply more environmentally friendly (so called “green”)fuels for automobiles and other uses has greatly increased the demandfor pressure vessels that can both store and be used in the transport ofthe fuels. Once of the most promising fuels today is CNG, and the needfor cost effective ways of producing pressure vessels for CNG vesselshas arisen.

Generally, the two most expensive features of a CNG pressure vessel arethe carbon fibers and the tank liners (around which the carbon fibersare wrapped). The cost of the carbon fibers is largely driven by thefree market and thus pressure vessel manufacturers can do little tocontrol or reduce the cost of the carbon fibers. Accordingly, reducingthe cost of the tank liners is desirable.

The most common types of pressure vessels used are: type 3 (metal lined)and type 4 (plastic lined) vessels. There is also a new type 5 vesselbeing considered by industry. The type 5 vessel is considered to beall-composite (no metallic or non-metallic liner). It may also beconsidered to be a type 5 vessel if it has a very thin permeationbarrier on the inside if it is also non-loadbearing. This disclosure canbe applied to a type 4 and/or a type 5 vessel. The common type 3 vesseltank liner is aluminum, but there are also some tank liners produced bywelded steel assemblies. The aluminum tank liner size limit iscontrolled by the diameter of available tube forgings. The diameter sizeusually stops around 18″. There are new emerging markets for trucks andbulk storage systems that need 25″ diameter tank liners or larger. Thisneed for the larger diameters has been one of the reasons that more type4 vessels are being developed. The manufacturing methods for the largertype 4 liners can be costly if there are frequent design changes becausethe molds and tooling are expensive. The new type 4 vessels however arelighter and cheaper than the aluminum liners for type 3 vessels.

The production of tank liners however, is not straight forward as itrequires specialized tooling and other equipment, and the costs of therequired equipment present a significant entry barrier in the industry.

The present disclosure provides a pressure vessel useful in thetransport and storage of gases and liquids, such as CNG that comprises atank liner with segments that can be bonded together. The pressurevessel of the present disclosure allows for modular manufacturing thatis cost effective and readily adaptable to change, more robust endfittings and domes.

BRIEF DESCRIPTION OF THE DRAWINGS

To further provide the advantages and features of the presentdisclosure, a more particular description of the invention will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings are not to be considered limiting in scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1A shows one embodiment of carbon fiber 20 having been overwrappedonto a tank liner 30.

FIGS. 1B and 1C show various embodiments of the permeation barrier ofthe present disclosure.

FIG. 2 shows one embodiment of a tank liner 30 disclosed herein.

FIG. 3 shows an alternate embodiment of a tank liner 30 disclosedherein.

FIG. 4 shows one embodiment of a plurality of pressure vessels 10 beingtransported inside of a protective enclosure 60.

DETAILED DESCRIPTION

The present disclosure provides a pressure vessel 10 (sometimes known asa composite overwrapped pressure vessel or “COPV”) comprising fibers 20(such as carbon fiber 20 filaments) wrapped around a tank liner 30. Thefibers 20 can also be used with embedded layers of fabric or othertextiles to enhance performance as needed as would be recognized by oneof skill in the art.

Any fiber 20 known in the art can be used with the pressure vessel 10disclosed herein. For example, typical carbon fiber 20 for pressurevessels 10 have a tensile strength about 700 kilo pounds per square inch(ksi) and a tensile modulus of about 33 million pounds per square inch(msi) or higher, so any material with similar characteristics may beused. Other fibers 20 overwraps include, but are not limited to, glassfiber, basalt fiber, jute twine, Zylon®, high-density polyethylene,polypropylene, polyethylene, nylon, Vectran® and high strength metalwire. In some embodiments, a carbon fiber 20 overwrap may also includean epoxy or a resin that acts to strengthen and harden the carbon fibers20. The present disclosure is not limited to a pressure vessel 10comprising a single type of fiber 20, accordingly, it is to beunderstood that the pressure vessel 10 may be wrapped (or overwrapped)with a plurality of different types of carbon fibers or other fibers 20,depending upon intended use and size of the pressure vessel 10. Oneexample of a tank liner 30 having been overwrapped and showing some ofthe carbon fibers 20 overwrapped onto the tank liner 30 is shown inFIG. 1. The fibers 20 may be wrapped at a continuous “depth” around thetank liner 30, or certain segments of the tank liner 30 may be wrappedwith thicker layers of fiber 20. For example, an area known to besubject to greater pressure may have more fibers 20 overwrapped than asection under less pressure. Alternatively, different types of fibers 20may be used on different areas of the pressure vessel subject todifferent pressures. Additionally, layering patterns may be used inconnection with the present disclosure, including without limitation,fibers 20 wound in helical layers, polar layers or hoop layers.Additionally, individual fibers 20 may be wound the same or differingangles relative to the tank liner depending upon the desired traits ofthe pressure vessel 10.

There are many suitable epoxies or resins that can be used in connectionwith the present disclosure. Some such resins are EPON® 828 and 862 andDow 383, and there are a variety of different curing agents andadditives that can be used to adjust the epoxy performance as needed.Additionally, the epoxy or resin can be impregnated onto the fibers 20before winding or the fibers 20 can be “wet wound” where the epoxy orresin is added as the fibers 20 is wound about the tank liner 30. Epoxyis the common resin matrix, but others can be used such as urethanes,polyureas, epoxy vinyl ester, bismaleimide and benzoxazine.

The present disclosure also provides a pressure vessel 10 with a noveltank liner 30. The tank liner 30 may have a variety of shapes (thusimparting a similar shape on the pressure vessel 10) includingspherical, cylindrical or conical. Of course, combinations of theaforementioned shapes are also within the scope of this disclosure. Inone embodiment, the tank liner 30 acts as a mandrel/tooling that holdsthe metal end fittings (discussed below) in place and it provides thesurface for the application of the permeation barrier. The compositemandrel tooling can rely on the permeation layer 50 (discussed below) tocontain the gasses and the mandrel can be viewed as fly-away tooling.

In one embodiment, the tank liner 30 comprises a plurality of segments40 that are bonded together. In an alternate embodiment, the tank liner30 is an integral structure comprising only one segment 40. The segments40 can be molded or shaped into a number of configurations. For example,as shown in FIG. 2, the tank liner 30 may comprise a plurality ofsegments 40 wherein one segment 42 forms the cylindrical body of thetank liner and two other segments 44 form the ends or dome caps of thetank liner. Alternatively, as shown in FIG. 3, the cylindrical body ofthe tank liner 30 may be comprised of several segments 42 a, 42 b thatare bonded together.

Depending upon the intended use of the pressure vessel 10, one or bothend segments 44 may comprise an end fitting 46 (typically but notexclusively, a hole drilled in the apex of the tooling for the capsegments that is then fitted with a metal fitting that interfaces withthe valve connection of a gas system) that is adapted to be connected toa valve or other mechanism useful for allowing the CNG to be vented fromthe pressure vessel 10. The metal end fitting can also be cast or woundin place with mandrel materials. Any end fitting known to those of skillin the art should be considered with the scope of this disclosure.Additionally, the type of end fitting may be varied depending upon theuse of the pressure vessel 10.

The segments 40 comprising the tank liner 30 may comprise many differentmaterials. In one embodiment, the tank liner 30 may be comprised of asingle material while in other embodiments the tank liner 30 may becomprised of a plurality of materials (for example, the end segments 44may be comprised of a different material than the segments 42 formingthe body of the tank liner 30). The composition of the tank liner 30 maybe varied depending upon the intended use of the pressure vessel 10. Inone application, the segments 42 and 44 may comprise glass fiberreinforced plastics. In an alternate embodiment the segments 42 and 44may comprise carbon fiber reinforced plastics. In alternateconstructions, the segments 42 may comprise a glass fiber reinforcedmaterial while the end segments 44 are metallic. If weight is critical,the composite tooling mandrel can be made with a carbon fiber and anepoxy matrix resin, or other resins. The composite end segments 44 andmetal end fittings 46 can also be outfitted with an-o-ring or sealantmaterial in the metal and non-metallic interfaces. An all-metallic endfitting 46 and end segment 44 is especially useful in extremely highpressure situations as the end fittings 46 are not bonded to the endsegment 44 but are rather an integral part of the end segment 44.

In the embodiments where the tank liner 30 comprises more than onesegment 40, the segments must be bonded to one another. The segments 40can have an overlapping joint allowing for a thin bond layer of adhesiveto bond the segments 40 together.

The tank liner 30 may be overwrapped directly by the carbon fiber 20 orit may first be covered by a permeation barrier 50 as shown in FIGS. 1Band 1C. The permeation barrier 50 can be on the inside, outside or bothside of the composite mandrel tooling depending on the application. Thepermeation barrier 50 may comprise a polymer such as polyurea orpolyurethane or other flexible materials The permeation barrier 50 canalso contain various fillers and additives to enhance the gas permeationproperties. In one embodiment the permeation barrier 50 may alsocomprise an additive such as nanoparticle that helps enhance itsperformance, such nanoparticles could include, but not be limited to,exfoliated clays or carbon nanotubes. This permeation barrier 50typically does not add strength to the structure it helps to keep thecontents of the pressure vessel 10 from leaking out. One of the mainfunctions of the permeation barrier 50 is to contain the gasses withinthe tank liner 30. The permeation barrier 50 can have several layers ofdifferent materials that are used to reduce the diffusion of the gasses.Once the permeation barrier 50 is added over the tank liner 30, thecarbon fiber 10 may be overwrapped using a traditional filament windingmachine. In one embodiment, the permeation barrier 50 may be interior tothe tank liner 30, then the tank liner 30 may be overwrapped with carbonfiber 10. In yet another alternate embodiment, there may be two (2)permeation barriers 50, one interior to the tank liner 30 and oneexterior to the tank liner 30.

The pressure vessel 10 of the present disclosure may be used in a numberof applications such as CNG powered automobiles, shipping CNG (by landor sea) or in rockets. Additionally, one or more of the pressure vessels10 disclosed herein may be included within, or surrounded by, aprotective enclosure 60 if the pressure vessels 10 are being used toship CNG. For example, four pressure vessels 10 may be surrounded by aprotective enclosure 60 as shown in FIG. 4.

Although particular embodiments of the present disclosure have beendescribed, it is not intended that such references be construed aslimitations upon the scope of this disclosure except as set forth in theclaims.

We claim:
 1. A pressure vessel comprising: a. a carbon fiber overwrap;b. a polymeric permeation barrier; and c. a tank liner, wherein the tankliner comprises fiber reinforced plastic.
 2. The pressure vessel ofclaim 1 wherein the polymeric material is selected from the groupconsisting of polyurethane and polyurea.
 3. The pressure vessel of claim2 wherein the permeation barrier further comprises a nanoparticleadditive.
 4. The pressure vessel of claim 3 wherein the nanoparticleadditive is selected from the group consisting of exfoliated clay andcarbon nanotubes.
 5. The pressure vessel of claim 1 wherein thepermeation barrier further comprises a nanoparticle additive selectedfrom the group consisting of exfoliated clay and carbon nanotubes. 6.The pressure vessel of claim 5 wherein the tank liner is an integralstructure.
 7. The pressure vessel of claim 6 wherein the tank linerfurther comprises carbon fibers.
 8. The pressure vessel of claim 7wherein the tank liner comprises a plurality of central segments and capsegments.
 9. The pressure vessel of claim 8 wherein the cap segments arecomprised of a metal.
 10. A pressure vessel comprising a tank linerwherein said tank liner further comprises fiber reinforced plastic. 11.The pressure vessel of claim 10 wherein the tank liner is an integralstructure.
 12. The pressure vessel of claim 10 wherein the tank linerfurther comprises carbon fibers.
 13. The pressure vessel of claim 12wherein the tank liner comprises a plurality of central segments and capsegments.
 14. The pressure vessel of claim 13 wherein the cap segmentsare comprised of a metal.
 15. The pressure vessel of claim 10 whereinthe tank liner is overlaid by a wound carbon fiber layer.
 16. Thepressure vessel of claim 15 wherein the wound carbon fiber layercomprises a carbon fiber having a tensile strength of about 700 KSI anda modulus approximately 33 MSI.
 17. The pressure vessel of claim 16,wherein the wound carbon fiber layer is of a uniform continuousthickness around the tank liner.
 18. The pressure vessel of claim 17further comprising a permeation barrier located between the tank linerand the wound carbon fiber layer.
 19. The pressure vessel of claim 18further comprising a second permeation barrier interior to a compositetooling/mandrel.